What is great is I draw these diagrams out myself. It took a while but what I ended up doing is drawing over a bunch of diagrams and use the old stock images lets call them like templates.
I'll put stuff in bold to make it easier to skim through as I like to be as descriptive as possible.
to use the outer 2 pickups or all 3 you want to include the 7 way mod. David has had it on his black strat since roughly 1972. They document his guitar really well on a website called gilmourish. I'm a big pink floyd fan myself. To do this use either a mini toggle or push pull potentiometer. If your tone control is say B250k, make sure your push pull pot is B250k and the guitar will react the same. Pickguards use 15mm potentiometers. On a classic vibe an import push pull will do the trick as it will not require any widening of the holes on the pickguard. The ones I used to get from IKNMusic (ebay) just remember to cut off the tab with some cheap wire cutters that keeps the pot on the pickguard I'll have to take a photo of what I mean. You would be able to still have control over the seperate tone controls.
To my understanding. Correct me if I'm wrong of course turning the middle tone in position 4 would warm up the entire guitar signal of both pickups.
there are other tone control alternatives such as the spin a split mod and so forth I'll get to at another reply. if warmth is an issue I've got you covered near the end
You can use 500k pots for the SSL-5
you could even use 1m (1000k). It affects the volume and brightness of the guitar. To see and experience this the easiest way if you've got a cheap guitar wire it up with just the volume and watch how the guitar reacts when turning the volume down. With just a 500k volume you'll notice the guitar is much brighter and as you turn the volume down to say half way is what 250k would sound like in a guitar. Not the best test and a waste of perfectly good solder but to prove a point.
I say try out what is in the guitar. If not a 500k pot for the single coil could work as I usually trust what the pickup makers were going for as I'm sure the SSL-5 was intended for 250k pots. However. Just like the infamous Seymour Duncan JB there is a ton of guys who go with different pot values to better suit their taste. At the end of the day it's how we play right or what we like.
David has had his black strat copper shielded. However if your guitar has the flat black paint and a ground loop drilled into it don't worry about it. The metal loop drilled in you'll see in FMIC (Fender) guitars such as Squiers and import Jackson guitars from India and Japan. If you don't use copper tape. Cover the entire guitar control cavity in it. If it's one of those guitars without a pickguard and individual routings similar to my washburn link them together with some wire and solder. Copper shielding and the conductive paint both provide more clairty. It won't eliminate 60 cycle hum but if people want to see a guitar without it one of those DHGate or similar "gibson" guitars are hornets nests without it even after a pickup swap to something people want from a local shop.
to get the most brightness out of the guitar for great clean tones the blower switch the internet calls it will help. This sends the guitar signal directly to the amp. It's not like going from another brick in the wall to marooned in terms of brightness but I found use out of it. Especially with the invader unless someone adjusted the pole pieces on the invader with an allen key the same one on floyd roses to lock the nuts or strings. I found the invader to be quite dark. Same principal applies to invaders. This is how to brighten one up.
https://www.youtube.com/watch?v=jXIggQxlAhc
This is how capacitors and potentiometers work in your guitar I have had this conversation probably 5-10 times a month at one time.
https://www.youtube.com/watch?v=ZCzZfKY2QM0&t=1s
Personally I'd grab a bunch of polyester capacitors from Tayda2009 (ebay) in a few different values. High end capacitors I wanted to believe in but assuming you get the same exact value when you measure them they do nothing with the lack of heat changes or anything even a cheap capacitor will do the same job a bumblebee or black beauty would. A lot of youtubers get one of each say a tropical fish, a ceramic disc (worst for guitars) , something from USSR and so forth all the same values and the difference you hear is the actual measurement of the capacitor as just because the capacitor says 0.022uf (22nf) the tolerance (accuracy) matters way more. If I got a bag of 0.047uf capacitors and measured them or put them on a varitone I'm sure people would hear a difference.
It's cheaper and easier to go above or below a recommended value. These are what I've usually got in stock for my projects. I'll focus on nanofarads as it's a bigger and easier to remember number.
0.01uf (10nf) , 0.022uf (22nf) 0.033uf (33nf) , 0.047uf (47nf) and 0.1uf (100nf)
say the pickup needs a slight bit more warmth - anything above 47nf
say a humbucker needs a slight bit more brightness - the lower than 47nf such as 22nf and 10nf - jimmy page for instance used 22nf and 15nf in some blogs I read in his les pauls
or just do this mod I mention all the time on here to get more brightness
View attachment 101498
anyways I think that is a good start for your questions. Keep them coming I actually enjoy answering questions like this. If anyone else wants to jump in go for it.